Process for the preparation of multicolored images by the silver dyestuff bleaching method



United States Patent 3,278,303 PROCESS FOR THE PREPARATION OF MULTI- COLORED IMAGES BY THE SILVER DYESTUFF BLEACHING METHOD Armin Meyer, Base], and Walter Anderau, Aesch, BasellLand, Switzerland, assignors to Ciba Limited, Basel, Switzerland, a company of Switzerland No Drawing. Filed Nov. 27, 1962, Ser. No. 240,458 Claims priority, application Switzerland, Dec. 20 ,1961, 14,837/ 61 17 Claims. (Cl. 96-20) The present invention provides a process for the preparation of multicolored photographic images by the silver dyestuff bleaching process. As is known, this process is based on the principle that dyestuffs, especially azo dye stuffs, are destroyed by an appropriate treatment in the presence of metallic silver. A treatment in a neutral to acid bath containing a complex-forming agent and a bleaching catalyst is known.

According to present opinion, the bleaching of the dyestuff should take place stoichiometrically depending on the silver present, in which process tour atoms of silver are required to destroy one azo group. It should thus be assumed that in material containing sevenal silver component images the gradations of the component color images are solely dependent on the gradations of the developed silver images. However, this is not the case. The gradations of the component color images are dependent on many other factors. For example, they are dependent on the nature of the individual dyestuffs, on the layer colloid, on the thickness of the layer, on the manner in which the silver is distributed within the layer and on the composition and duration of action of the bleaching bath.

Suggestions have already been made for controlling the gradations of the component color images independently, especially for making them. flatter; for example, by incorporating non-diffusing bleaching catalysts into the lightsensitive layers, by the use of oxidizing agents in the bleaching process or by the use of several dyestuff bleaching baths.

This invention is based on the surprising observation that in the preparation of multi-colored photographic images by the silver dyestuff bleaching process especially advantageous effects can be obtained with the use of catalysts if the exposed photographic material is treated, be-v fore bleaching, in a non-developing and non-bleaching bath to which has been added a dyestutf bleaching catalyst capable of diffusion.

The photographic material to be used may, for example, comprise a layer support, and three layers of a hydrophilic colloid such as gelatin, one layer being dyed cyan, one magenta and the other yellow, each of which contains a developed silver image. The layers may also be in a different sequence. Instead of the layers the material may contain colored particles in the manner of the mixed grain emulsions; the support can be transparent or reflecting, and other layers such as adhesive layers, intermediate layers, filter layers and covering layers may also be present. The said material can contain the usual emulsion additions such as wetting agents, optical and chemical sensitizers and, in one or more layers or intermediate layers, small amounts of bleaching catalyst.

The dyestuff bleaching bath consists normally of an acidic aqueous solution, for example, hydrochloric acid and at least one complex-forming agent, for example, potassium bromide or thiourea. This bath can likewise contain a small amount of a bleaching catalyst. However, the amounts of catalyst that may be present in the material and/ or in the bleaching bath must be calculated in such a manner that there is not enough to bring about complete bleaching of all dyestuffs by the image silver that is present in the time available.

The non-developing bath containing the bleaching catalyst can be, for example, a so-called stop bath, a hardening bath, a neutral or slightly acid fixing bath or a special bath. Advantageously the catalyst is added to the fixing bath or to the special bath that follows the fixing bath. This special bath can consist of a neutral aqueous solution of the catalyst and a wetting agent. Since the catalyst diffuses slowly, the material can be washed with water after the bath containing the catalyst and before the bleaching bath.

Suitable bleaching catalysts are known; quinoxalines, phenazines, quinolines, alloxazines and cinnoline can be used as bleaching catalysts.

Thus, an advantageous method of carrying out the process consists in exposing and developing a light-sensitive, rnulti-layer material colored with azo dyestuffs but not containing a bleaching catalyst in the usual manner, fixing it in a bath containing a thiosulfate and a bleaching catalyst and then, after intermediate washing with water, bleaching it in a bath free from a catalyst, and finally freeing it from the remaining silver in the usual manner.

In the present process the catalyst acts in a very even manner in the various layers and behaves favourably in respect of diffusion, so that no over bleaching of the top layers takes place, as is the case in the usual processes.

Finally, in contradistinction to the known methods, the gradations of the single dyestuffs in the process of the invention are adjusted in such a manner that flat, parallel color gradation curves are obtained on exposure to white light, and steep gradation curves are obtained on exposure to the light of only one color of the spectrum. Thus, when a color chart that also includes a neutral wedge is copied an image is obtained in which the grey portion is correctly reproduced and in which the colors show a high degree of chromaticity. Should this process lead to too extensive a bleaching of the lower layers, this can be compensated by dividing the catalyst between the preliminary bath and the dyestuff bleaching bath.

Unless otherwise stated, the parts and percentages in the following examples are by weight.

Example 1 To a cellulose acetate film provided with an adhesive layer the following layers are applied one after the other:

(1) A red-sensitive silver bromide emulsion in gelatine containing the cyan dyestulf of the formula (2) Agelatine intermediate layer. bath containing the catalyst was omitted and the same (3) A green-sensitive silver bromide emulsion in catalyst (2 mg. per liter of bleaching bath) was added gelatine containing the magenta dyestutf of the formula to the dyestuif bleaching bath. In this case, 7 minutes (2) NH; H038 SOIH HZN OH HO HOi S SOzH (4) A yellow filter layer containing the dyestuif of were necessary in the dyestuff bleaching bath in order the formula to just complete the bleaching. (3) $031; The results obtained in the comparative experiments in respect of gradation (gamma values) and exposure 0 I CH, bqe 15 value, the exposure value being expressed by A 10g 5 N(:H=c I are given in the following tabl C6g \C= l A log E=10g E 1 Emin N in which E and E represent, respectively, the

strongest and weakest exposures that are technically possible in copying. The color densities were measured in transmitted light by means of a Macbeth-Ansco Desitom- (5 A blue-sensitive silver bromide emulsion in gelatine containing the dyestutf of the formula Has 0 s 0 H soul Ho s and, as precipitating agent, a mixture consisting of a eter; the gamma values correspond to the straight sections reaction product of dicyanodiamidine and formaldehyde, of the gradation curves. a small proportion of sodium forinate and sodium bisulfate.

(6) Agelatineprotective layer. c lg tmb gercgt igIhgsltinhqyemeiae at su eac ng This film is exposed four times behind a neutral grey wedge used Filter bath wedge namely (1) with red light only, (2) with green light only, (3) with blue light only, and (4) with red, green and blue light, in which process the exposures are Gamma A m D Gamma A M D adjusted in such a manner that the fourth wedge appears 40 R ed-.-" 0.8 1.9 0.9 1.4 as aneutral y- Grey wedge (331mm-.. l ,7 s v I The images obtained are hereinafter called red wedge, Red wedge ai 09 1 A 1 1 green Wedge, e Wedge and grey Wedge. Green wedge Green-.- 1.1 1.5 1.2 1.2 After being hardened in a formaldehyde bath, the Bluewedge Blue-m film is developed in a Metol hydroquinone developer, and then treated in an acetic acid stop bath and fixing l bath containing thiosulfate. After being washed with Results analo to ihosfi Obtalned 1n the experlmel'lt water, the film is treated for 10 minutes in a bath conwith the catalyst in the intermediate bath are obtained taining 3 mg. of 2-amino-3-hydroxyphenazine hydrowhen the bleaching catalyst is present in the first fixmg chloride per liter and to which could be added 4 cc. of a bath. A similar result is also obtained when a form- 1.25% solution of the addition product of 35 mols of aldehyde hardening bath containing a small proportion ethylene oxide and 1 mol of octadecyl alcohol to improve of catalyst is interposed between the first fixing bath Wetting. and the dyestuff bleaching bath. After an intermediate washing with water lasting 5 The dyestuff in the red-sensitive layer may be preminutes, the film is treated for 3% minutes in the following pared as follows: dyestulf bleaching bath: 198 parts of 1-amino-2:5-dimethoxy-4-nitrobenzene are diazotized in a suspension acidified with hydrochloric rigizi s bromlde '"I i8 acid and the diazo compound so obtained is coupled with Hydrochloric acid (36% Strength) "cc" 361 parts of 1-acetylamino-8-hydroxynaphthalene-3zo-dt- 1.25% solution of the addition product of 35 mols 6O .Sulfonic i The p q dyestufi so Obtamed of ethylene oxide and 1 mol of octadecyl is reduced in an alkaline bath with sodlum sulfide to form alcohol cc" 10 the amlnomonoazo dyestuff. ThlS dyestuff 1s purified by Made up with water to 1000 recrystallization, diazotized, and the diazo compound coupled with 542 parts of l-(4-benzoylamino-benzoylamino)- The film is then Washed with Water, the residual silver 5 8-hydroxynaphthalene-3:6-disulfonic acid in a mixture of rehalogenated with a copper nitrate hath made strongly pyridine and aqueous ammonia. The disazo dyestuif so acidic with hydrochloric acid, the film washed again with obtained is freed from violet-colored impurities by rewater, fixed a second time, again washed with water and peated recrystallization.

then dried. The time to be taken for bleaching is deter- The dyestulf in the green-sensitive layer is prepared by mined by experiment and is just sufficient to bleach the 70 coupling diazotized 1-amino-4-nitrobenzene-2 -sulfonic dyestuffs completely in all the layers at areas that. had acid with 2-amino-8-hydroxynaphthalene-6-sulfonic acid been highly exposed. in an acid medium, reducing the nitroazo dyestutf and For comparison purposes, a series of four exposures obcondensing with 4-nitrobenzoylchloride, reducing the tained in the same manner is described above were treated nitroazo dyestuff to form the aminoazo dyestuff and rein the same manner as above, except that the intermediate acting with phosgene to form the urea derivative.

The dyestutf in the yellow filter layer is prepared as follows:

9.7 g. of l-(2'-chloro-5-sulfonphenyl) 3 methylpyrazolone are dissolved in 160 cc. of water, the pH of the solution being adjusted to 6.0 by the addition of sodium hydroxide solution, and the solution is heated to 70 C. under reflux. To this solution is added in the course of 5 minutes, while stirring, a solution of g. of paradibenzylaminobenzaldehyde in 200 cc. of 96% alcohol heated to 70 C. and containing 0.2 cc. of piperidine. The reaction mixture is then stirred for minutes at the boil, cooled to room temperature, and allowed to stand for 16 hours.

After separating off the small proportion of unreacted para-dibenzylaminobenzaldehyde, the solution is completely evaporated in vacuo at 50 to 80 C. The orangecolored crude dyestutf (84 g.) is purified by recrystallization from alcohol.

Example 2 The same procedure is adopted as described in Example 1, but using, after fixing and subsequent washing with Water, instead of the bath containing 2-amino-3-hydroxy phenazine hydrochloride, a bath containing 4 cc. of a 1.25% solution of the addition compound of 35 rnols of ethylene oxide and 1 mol of octadecyl alcohol per liter, and one of the following catalysts:

(a) mg. of 2:3-diaminophenazine.

(b) 200 mg. of riboflavin.

(c) 600 mg. of Z-methylquinoxaline.

(d) 200 mg. of 2,: 3-dimethylquinoxaline.

(e) 100 mg. of 2-amino-3-hydroxyphenazine-x-sulfonic acid.

(f) 50 mg. of 5:5'-dihydroxy-dinaphthazine-(1:1- 2:2)-7:7'-disulfonic acid of the formula (5) H038 SOQH HO- OH (g) 30 mg. of the azine compound of the formula Complete bleaching is obtained in all cases. Combinations of these catalysts also yield good results.

The 2-amino-3-hydroxyphenazine-x-sulfonic acid (e) can be obtained by sulfonating 2-amino-3-hydroxyphenazine with fuming sulfuric acid.

The azine compound of the Formula 6 is obtained when the monoazo dyestuff prepared by coupling diazotized l-aminobenzene-4-sulfonic acid and Z-phenylamino-S-hydroxynaphthalene-7-sulfonic acid in an acid medium is heated in a strongly acid medium (hydrochloric acid,

6 pH=0.8) for 1 hour at to 90 C. and the compound obtained of the formula H0 aI is coupled in an alkaline medium With diazotized l-aminobenzene-4-sulfonic acid.

The azine compound of the Formula 7 may be prepared as follows: 0.1 mol of the compound of Formula 6 is dissolved in 860 cc. of 1 N-sodium hydroxide and 78 g. of 82% sodium hydrosulfite added at 70 C. in the course of 5 minutes. As soon as the reaction mixture is turned yellow-brown, concentrated hydrochloric acid is added until a strong Congo-acid reaction is obtained. The resulting precipitate is filtered off and washed free from acid with water. The gray-green residue is dissolved in a dilute solution of sodium hydroxide, and the pH value adjusted to 6.5 with acetic acid. The product is then salted out with sodium acetate, filtered off, dissolved in water to purify it further, the impurities filtered off and sodium chloride added. The crystalline precipitate is suction-filtered and then dried in vacuo at 40 to 50 C. A dark-brown powder is obtained. The yield is about 85% of the theoretical.

What is claimed is:

1. In a process for the preparation of multi-colored photographic images by the silver dyestuif bleaching method with the aid of a catalyst, the step which comprises treating the exposed photographic material before the dyestuff bleaching operation in a non-developing and non-bleaching bath to which has been added a dyestuff bleaching catalyst that is capable of diffusing.

2. In a process for the preparation of multi-colored photographic images by the silver dyestuff bleaching method with the aid of a catalyst, the step which comprises treating the exposed photographic material before the dyestutf bleaching operation in a bath for fixing the silver image which bath contains a dyestuff bleaching catalyst that is capable of diffusing.

3. In a process for the preparation of multi-colored photographic images by the silver dyestuff bleaching method with the aid of a catalyst, the step which comprises treating the exposed photographic material before the dyestulf bleaching operation in a hardening bath which contains a dyestuif bleaching catalyst that is capable of diffusing.

4. In a process for the preparation of multi-colored photographic images by the silver dyestuff bleaching method with the aid of a catalyst, the step which oomprises treating the exposed photographic material after the treatment with the fixing bath and before the dyest utf bleaching operation in a special bath which contains a dyestuff bleaching catalyst that is capable of diffusing.

5. In a process for the preparation of multi-oolored photographic images by the silver dyestuff bleaching method with the aid of a catalyst, the step which comprises treating the exposed photographic material before the dyestuff bleaching operation in a bath for fixing the silver image which bath contains as .a dyestulf bleaching catalyst an azine compound that is capable of diffusing.

6. In a process for the preparation of multi-oolored photographic images by the silver dyestuff bleaching method with the aid of a catalyst, the step which comprises treating the exposed photographic material before the dyestuif bleaching operation in a hardening bath which contains as a dyestulf bleaching catalyst an azine compound that is capable of diffusing.

7. In a process for the preparation of multi-colored photographic images by the silver dyestuff bleaching method with the aid of a catalyst, the step which comprises treating the exposed photographic material after the treatment with the fixing bath and before the dyestufi bleaching operation in a special bath which contains as a dyestuff bleaching catalyst an azine compound that is capable of diffusing.

8. In a process for the preparation of multi-colored photographic images by the silver dyestuff bleaching method with the aid of a catalyst, the step which comprises treating the exposed phot-ographic material before the dyestutf bleaching operation in a bath for fixing the silver image which bath contains as a dyestutf bleaching catalyst a phenazine compound that is capable of diffusing.

9. In a process for the preparation of multi-colored photographic images by the silver dyestuff bleaching method with the aid of a catalyst, the step which comprises treating the exposed photographic material before the dyestulf bleaching operation in a bath for fixing the silver image which bath contains 2-amino-3-hydroxyphenazine as a dyestulf bleaching catalyst.

10. In a process for the preparation of multi-colored photographic images by the silver dyestulf bleaching method with the aid of a catalyst, the step which comprises treating the exposed photographic material before the dyestutf bleaching operation in a bath for fixing the silver image which bath contains 2:3-diaminophenazine as a dyestufi" bleaching catalyst.

11. In a process for the preparation of multi-colored photographic images by the silver dyestutf bleaching method with the aid of a catalyst, the step which comprises treating the exposed photographic material before the dyestuff bleaching operation in a bath for fixing the silver image which bath contains riboflavin as a dyestuff bleaching catalyst.

12. In a process for the preparation of multi-colored photographic images by the silver dyestuff bleaching method with the aid of a catalyst, the step which comprises treating the exposed photographic material before the dyestuff bleaching operation in a bath for fixing the silver image which bath contains Z-methylquinoxaline as a dyestuff bleaching catalyst.

13. In a process for the preparation of multi-colored photographic images by the silver dyestuff bleaching method with the aid of a catalyst, the step which comprises treating the exposed photographic material before the dyestutf bleaching operation in a bath for fixing the silver image which bath contains 2:3-dimethylquinoxaline as a dyestufi bleaching catalyst.

14. In a process for the preparation of multi-colored photographic images by the silver dyestuff bleaching method with the aid of a catalyst, the step which comprises treating the exposed photographic material before the dyestutf bleaching operation in a bath for fixing the silver image which bath contains 2-amino-3-hydroxyphenazine-sulfonic acid as a dyestutf bleaching catalyst.

15. In a process for the preparation of multi-col-ored photographic images by the silver dyestutf bleaching method with the aid of a catalyst, the step which comprises treating the exposed photographic material before the dyestuff bleaching operation in a bath for fixing the silver image which bath contains the azine compound of the formula ,as a dyestuflf bleaching catalyst.

16. In a process for the preparation of multi-colored photographic images by the silver dyestuif bleaching method with the aid of a catalyst, the step which comprises treating the exposed photographic material before the dyestutf bleaching operation in a bath for fixing the silver image which bath contains the azine compound of the formula HOaS as a dyestufi bleaching catalyst.

17. In a process for the preparation of multi-colored photographic images by the silver dyestutf bleaching method with the aid of a catalyst, the step which comprises treating' the exposed photographic material before the dyestuff bleaching operation in a bath for fixing the silver image which bath contains the azine compound of the formula as a dyestutf bleaching catalyst.

References Cited by the Examiner NORMAN G. TORCI-IIN, Primary Examiner.

A. D. RICCI, Assistant Examiner. 

1. IN A PROCESS FOR THE PREPARATION OF MULTI-COLORED PHOTOGRAPHIC IMAGES BY THE SILVER DYESTUFF BLEACHING METHOD WITH THE AID OF A CATALYST, THE STEP WHICH COMPRISES TREATING THE EXPOSED PHOTOGRAPHIC MATERIAL BEFORE THE DYESTUFF BLEACHING OPERATION IN A NON-DEVELOPING AND NON-BLEACHING BATH TO WHICH HAS BEEN ADDED A DYESTUFF BLEACHING CATALYST THAT IS CAPABLE OF DIFFUSING. 